Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.50	3.610%	$151.7887	$151.79	$151.80	$151.80
Purchase #2	$152.54	3.257%	$157.5082	$157.51	$157.50	$157.50
Purchase #3	$141.86	13.122%	$160.4749	$160.47	$160.45	$160.50
Purchase #4	$176.27	13.850%	$200.6834	$200.68	$200.70	$200.70
Purchase #5	$243.27	13.654%	$276.4861	$276.49	$276.50	$276.50
Purchase #6	$161.80	3.219%	$167.0083	$167.01	$167.00	$167.00
Purchase #7	$24.71	9.730%	$27.1143	$27.11	$27.10	$27.10
7 purchase totals =	$1,046.95		$1,141.0639	$1,141.06	$1,141.05	$1,141.10